[GitHub] [arrow-rs] viirya commented on a diff in pull request #4259: Extract IPC ArrayReader struct

["viirya (via GitHub)" <gi...@apache.org>]

viirya commented on code in PR #4259:
URL: https://github.com/apache/arrow-rs/pull/4259#discussion_r1201092414


##########
arrow-ipc/src/reader.rs:
##########
@@ -628,14 +395,108 @@ fn create_dictionary_array(
     }
 }
 
+/// State for decoding arrays from an encoded [`RecordBatch`]
+struct ArrayReader<'a> {
+    /// Decoded dictionaries indexed by dictionary id
+    dictionaries_by_id: &'a HashMap<i64, ArrayRef>,
+    /// Optional compression codec
+    compression: Option<CompressionCodec>,
+    /// The format version
+    version: MetadataVersion,
+    /// The raw data buffer
+    data: &'a Buffer,
+    /// The fields comprising this array
+    nodes: VectorIter<'a, FieldNode>,
+    /// The buffers comprising this array
+    buffers: VectorIter<'a, crate::Buffer>,
+}
+
+impl<'a> ArrayReader<'a> {
+    fn next_buffer(&mut self) -> Result<Buffer, ArrowError> {
+        read_buffer(self.buffers.next().unwrap(), &self.data, self.compression)
+    }
+
+    fn skip_buffer(&mut self) {
+        self.buffers.next().unwrap();
+    }
+
+    fn next_node(&mut self, field: &Field) -> Result<&'a FieldNode, ArrowError> {
+        self.nodes.next().ok_or_else(|| {
+            ArrowError::IoError(format!(
+                "Invalid data for schema. {} refers to node not found in schema",
+                field
+            ))
+        })
+    }
+
+    fn skip_node(&mut self, field: &Field) -> Result<(), ArrowError> {

Review Comment:
   I feel original name `skip_field` is more proper, but okay for `skip_node`.



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